Two different methods for CuO powder, mounting using adhesive tape and compressed powder pellets were compared as to how these methods influence the XPS measurements. In Ar⁺ sputtering, these methods showed differences in the extent of selective sputtering by oxygen and the reduction rate. In a long period of sputtering, the reduction rate was greater with the powders mounted on tapes than with those compressed into pellets. During data acquisition, the amount of carbon on the sample surface on the tape increased with time to a greater extent compared with the pellet sample surface. This is interpreted in terms of the contamination from the tape materials. In addition, the pellet samples gave nearly twice the signal intensity of the samples on tapes and a smaller FWHM value of Cu2p_3/2 peak by approximately 0.05eV. These results indicate that the pellet method is better than the tape method in terms of low contamination, signal intensity and energy resolution.